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Improving the selectivity in the oxidative coupling of methane to ethane/ethylene poses a significant challenge for commercialization. The required improvements are hampered by the uncertainties associated with the reaction mechanism due to its complexity. Herein, we report about 90 % selectivity to the target products at 11 % methane conversion over Gd2O3‐based catalysts at 700 °C using N2O as the oxidant. Sophisticated kinetic studies have suggested the nature of adsorbed oxygen species and their binding strength as key parameters for undesired methane oxidation to carbon oxides. These descriptors can be controlled by a metal oxide promoter for Gd2O3. [ABSTRACT FROM AUTHOR]

Heterogeneous thermal-catalytic CO2 hydrogenation to alcohols using renewable energy is a highly attractive approach for recycling greenhouse gases into high-value chemicals and fuels, thereby reducing the dependence on fossil fuels, while simultaneously mitigating the CO2 emission and environmental problems. Currently, great advances have been made on the heterogeneous catalysts, but an in-depth and more comprehensive understanding to further promote this reaction process is still lacking. Herein, we highlight the thermodynamic and kinetic analysis of CO2 hydrogenation reaction firstly. Then, various reaction pathways for CO2 hydrogenation to methanol and higher alcohols (C2+ alcohols) have been discussed in detail, respectively, by combining the experimental studies and density functional theory calculations. On this basis, the key factors influencing the reaction performance, such as metal dispersion, support modification, promoter addition and their structural optimization, are summarized on the metal-based and metal-oxide-based catalysts. In addition, the catalytic performance of CO2 hydrogenation to alcohols and the relationship between structure and properties are mainly summarized and analyzed in the past five years. To conclude, the current challenges and potential strategies in catalyst design, structural characterization and reaction mechanisms are presented for CO2 hydrogenation to alcohols. [ABSTRACT FROM AUTHOR]

The present study of oxidative coupling of methane (OCM) over MnOx−Na2WO4/support catalysts demonstrated that the selectivity to C2H6 and C2H4 (C2‐hydrocarbons) is affected by the kind of support, co‐fed water, and the kind of oxidant (O2 vs. N2O). In addition to previous studies with MnOx−Na2WO4/SiO2, an enhancing water effect was obtained using catalysts based on TiO2‐ or ZrO2‐containing supports. However, a negative effect on methane conversion was established for SiO2−Al2O3‐supported catalysts. Temporal analysis of products with isotopic tracers suggests that the ability of MnOx−Na2WO4 to generate diatomic adsorbed oxygen species depends on the kind of support and is the key property for the water effect. The strength of the water effect on the activity decreases with an increase in the surface area of working catalysts. The kind of support also affects products selectivity due to its influence on the mobility/releasability of lattice oxygen in supported MnOx−Na2WO4. Among the prepared catalysts, MnOx−Na2WO4/TiO2 was found to be promising for H2O‐assisted OCM. The use of N2O instead of O2 further increases the selectivity to C2‐hydrocarbons to 84 % at 6.8 % CH4 conversion due to the formation of predominantly monoatomic oxygen species from N2O that selectively convert CH4 into C2H6. [ABSTRACT FROM AUTHOR]

This work built a molecular‐level kinetic model for hydrocarbon catalytic cracking, incorporating the catalyst acidity as the parameter to estimate reaction rates. The n‐decane and 1‐hexene co‐conversion catalytic cracking process was chosen as the studying case. The molecular reaction network was automatically generated using a computer‐aided algorithm. A modified linear free energy relationship was proposed to estimate the activation energy in a complex reaction system. The kinetic parameters were initially regressed from the experimental data under several reaction conditions. On this basis, the product composition was evaluated for three catalytic cracking catalysts with different Si/Al. The Bronsted acid and Lewis acid as the key catalyst properties were correlated with kinetic parameters. The built model can calculate the product distribution, gasoline composition, and molecular distribution at different reaction conditions for different catalysts. This sensitive study shows that it will facilitate the model‐based optimization of catalysts and reaction conditions according to product demands. [ABSTRACT FROM AUTHOR]

The efficient and clean conversion of light alkanes is a research hotspot in the petrochemical industry, and the development of effective and eco-friendly non-noble metal-based catalysts is a key factor in this field. Among them, gallium is a metal component with good catalytic performance, which has been extensively used for light alkanes conversion. Herein, we critically summarize recent developments in the preparation of gallium-based catalysts and their applications in the catalytic conversion of light alkanes. First, we briefly describe the different routes of light alkane conversion. Following that, the remarkable preparation methods for gallium-based catalysts are discussed, with their state-of-the-art application in light alkane conversion. It should be noticed that the directional preparation of specific Ga species, strengthening metal-support interactions to anchor Ga species, and the application of new kinds of methods for Ga-based catalysts preparation are at the leading edge. Finally, the review provides some current limitations and future perspectives for the development of gallium-based catalysts. Recently, different kinds of Ga species were reported to be active in alkane conversion, and how to separate them with advanced in situ and ex situ characterizations is still a problem that needs to be solved. We believe that this review can provide base information for the preparation and application of Ga-based catalysts in the current stage. With these summarizations, this review can inspire new research directions of gallium-based catalysts in the catalysis conversion of light alkanes with ameliorated performances. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co/ZrO 2 catalysts with single Co2+ are efficient for C 3 H 8 dehydrogenation to C 3 H 6. • 1Co/ZrO 2 performed durable over multiple dehydrogenation/regeneration cycles. • 1Co/ZrO 2 showed higher activity than a commercial analogue of K-CrO x /Al 2 O 3. • The high activity results from a synergy effect between Co2+ and Zr cus. • Recombination of surface H species is the rate-limiting step in C 3 H 6 formation. Due to the increased production of shale gas containing propane, the share of non-oxidative propane dehydrogenation (PDH) in the large-scale production of propene is expected to continue to grow. There are, however, some ecofriendly and cost shortcomings associated with the currently applied Cr- or Pt-containing catalysts. Against this background, we present here Co/ZrO 2 alternatives and reveal the fundamentals affecting their activity, which can be used for purposeful catalyst design. Co2+ species homogeneously distributed within the lattice of ZrO 2 significantly increase the activity of coordinatively unsaturated Zr4+ for the PDH reaction. The increase is caused by accelerating both the cleavage of CH bonds in propane and the recombination of surface H species, with the latter reaction being the rate-limiting step. The best-performing catalyst outperformed an analogue of commercial K-CrO x /Al 2 O 3 in terms of the rate of propene formation and demonstrated durable performance over a series of 10 PDH/regeneration cycles under industrially relevant conditions. It also outperformed most previously developed Co-containing catalysts in terms of propene productivity. The space–time yield of propene formation achieved at 57 % equilibrium propane conversion at 550 °C was 0.71 kg·h−1·kg cat -1. [ABSTRACT FROM AUTHOR]

The article titled "Elucidating the Role of Oxygen Species in Oxidative Coupling of Methane over Supported MnOx-Na2WO4-containing Catalysts" in the journal ChemCatChem explores the main products of the oxidative coupling of methane reaction over different catalysts. The researchers found that a low catalyst surface area and low reactivity of support lattice oxygen are beneficial for achieving high selectivity to C2H6 and C2H4. The TiO2 support meets these requirements, while Al2O3 and ZrO2 supports predominantly produce CO or CO2. The selectivity to desired products over TiO2-supported catalysts can be improved by replacing O2 with N2O and/or co-feeding H2O to reduce the concentration of adsorbed diatomic oxygen species. [Extracted from the article]

[Display omitted] • Metallic Co0 species in situ formed are suggested to be the main active sites for PDH. • CoO x but not Co0 is responsible for the formation of undesired products. • Transformation of CoO x to Co0 depends on the strength of CoO x -support interactions. • Co/Silicalite-1 showed the C 3 H 6 space time yield of 1.50 kg·h−1·kg cat −1 at 550 °C. Although Co-containing catalysts show attractive performance in the non-oxidative propane dehydrogenation to propylene (PDH), their tailored development is hindered by the ambiguity in the kind of active sites (Co0 or Co2+O x) responsible for selective and unselective pathways. Herein, we demonstrate that supported CoO x species expends its lattice oxygen through oxidation of C 3 H 8 to CO 2 /C 3 H 6 and are accordingly transformed into Co0 species. The latter are decisive for the selective dehydrogenation of propane to propylene with high activity. The ability of CoO x to in situ form Co0 is affected by metal-oxide-support interactions (MOSI). In addition to the kind of support, defective OH groups (OH nests) in ZSM-5-type zeolites seem to be relevant for the MOSI effect. In comparison with previous studies highlighting the importance of the size of CoO x species and their acidity for coke formation, we could not establish any direct correlation. Nevertheless, the presence of CoO x seems to be relevant for this undesired reaction because the formation of coke is hindered when CoO x species are transformed to Co0 species. Catalyst acidic sites are responsible for cracking reactions. Thus, the derived mechanistic insights reveal the nature of active sites both for selective and unselective pathways and provide fundamentals for catalyst development. From an industrial viewpoint, the developed Co/Silicalite-1 (Co/S-1) catalyst with the weakest MOSI and accordingly highest fraction of Co0 showed the space time yield of propylene formation of 1.50 kg·h−1·kg cat −1 at 67 % equilibrium propane conversion and propylene selectivity of 95.3 % and the Co-related TOF value of 0.145 s−1 at 550 °C. These both activity values exceed those of the state-of-the-art Co-containing catalysts. The productivity of Co/S-1 is comparable or even higher than that of industrially relevant Pt- or Cr-containing catalysts. [ABSTRACT FROM AUTHOR]

• Activity and stability of Ga/ZSM-5 were improved by H 2 -O 2 treatment. • Effective balance of dehydrogenation and cracking of Ga/ZSM-5 was achieved. • Activation energy was decreased largely for Ga/ZSM-5 after H 2 -O 2 treatment. • The mechanism of butane-O 2 treatment on Ga/ZSM-5 was proposed. Ga species with high dehydrogenation capability were prepared by H 2 -O 2 atmosphere treatment, and efficient balance of bifunctionality (dehydrogenation/cracking) was realized between Ga species and ZSM-5 over Ga/ZSM-5 based catalysts. Compared with parent Ga/ZSM-5, the conversion rate of n -butane was increased from 0.53 to 2.59 mmol·g−1·min−1 on Ga/ZSM-5 with H 2 -O 2 treatment. Kinetic analysis revealed that the apparent activation energy of n -butane catalytic cracking decreased largely from 141 to 47 kJ·mol−1, which is attributed to the formation of new interaction between Ga species and ZSM-5 upon such an atmosphere treatment. It was also found Butane-O 2 treatment acted as a similar role with H 2 -O 2 treatment in enhancing the catalytic performance. On this basis, different Ga species were correlated with activity and kinetic data, and the effect of practical reaction atmosphere on Ga species was also investigated. [ABSTRACT FROM AUTHOR]

[Display omitted] • Alkali metal in MnO x -M 2 WO 4 /SiO 2 affects activity under anaerobic conditions. • Lattice oxygen of MnO x -M 2 WO 4 /SiO 2 can convert CH 4 to hydrocarbons. • OCM over MnO x -M 2 WO 4 /SiO 2 and M 2 WO 4 /SiO 2 proceeds via adsorbed oxygen species. • Presence of MnO x does not create more active sites but changes their reactivity. This work unveils the fundamentals relevant for activity and product selectivity in the oxidative coupling of methane (OCM) over the (MnO x)-M 2 WO 4 /SiO 2 (M = Na, K, Rb, or Cs) catalysts. The presence of the molten phase of Na 2 WO 4 and the ability of the catalysts to release lattice oxygen were not found to be the performance-governing factors. As proven by oxygen isotopic exchange experiments combined with thorough catalytic tests, the performance of both tri- and bimetallic catalysts is defined by the involvement of adsorbed oxygen species formed from gas-phase O 2. Lattice oxygen of M 2 WO 4 /SiO 2 is not capable of converting CH 4 to C 2 H 6 , while that of MnO x -M 2 WO 4 /SiO 2 is active for this reaction. The OCM activity of M 2 WO 4 /SiO 2 decreases with the atomic weight of alkali metal, whereas there is no such effect in the presence of MnO x , which, however, increases the activity. The enhancing effect was explained by improving the active site turnover. [ABSTRACT FROM AUTHOR]

[Display omitted] • The dependence of the rate of propene formation on Ga/Zr ratio over Ga 2 O 3 /ZrO 2 was determined for PDH. • The reaction intermediates and mechanism were studied by in-situ DRIFTS and DFT calculations. • GaⅡ–O 3c Ⅱ structure was determined as the active site with enhanced C–H bond activation ability over Ga 2 O 3 /ZrO 2. • Ga 2 O 3 /ZrO 2 catalyst showed a good reaction-regeneration stability. ZrO 2 -based catalysts have attracted extensive attention in propane dehydrogenation (PDH) owing to their environmental compatibility, low costs, and superior catalytic performance. However, the structure–activity relationship and mechanistic analysis of Ga 2 O 3 /ZrO 2 in PDH are rarely studied where GaO x either acts as an active site or a promoter. Here, Ga 2 O 3 /ZrO 2 catalysts with different Ga/Zr ratios were synthesized by the impregnation technique, and the structure–activity relationship was revealed by combining complementary in/ex-situ characterization methods with catalytic tests. It is found the rate of propene formation first increases linearly and then reaches a plateau with the increase of Ga 2 O 3 loading, such activity-loading dependence is related to the evolution of Ga 2 O 3 species varying from monodisperse to single-layer and then multilayer states. Activation energy and C 3 H 8 -TPSR results suggest the formation of a new active site with high intrinsic activity over Ga 2 O 3 /ZrO 2. Furthermore, the molecular level reaction mechanism of Ga 2 O 3 /ZrO 2 in PDH was studied by DFT calculations, which pointed out the active site structure was GaⅡ–O 3c Ⅱ site exhibiting enhanced activation ability toward C–H bond and lower reaction barrier compared with bare ZrO 2. This work is expected to offer new insights into understanding the structure–activity relationships over ZrO 2 -based catalysts for PDH reaction. [ABSTRACT FROM AUTHOR]